As panels of multiple genetic tests become increasingly available, clinicians face new challenges in helping patients understand the nature of these tests. Diagnostic tests for conditions that inevitably lead to disease, "susceptibility" tests that reveal heightened risk of disease, and tests for carrier status raise different concerns about informed consent and pose different needs for counseling. Clinicians must understand the implications of different kinds of tests, and of different arrays of tests in multiple panels, if multiplex tests are to be used wisely in clinical practice.